Evaluation of Switching Gain:
Evaluation of \(\rho \)  like () is conservative in nature and evidently requires the knowledge of \(\Theta ^{*}\) , which is not always possible in the face of uncertain parametric variations and external disturbances.
The control laws developed in [1]}-[2]} and [3]}-[4]} assume that \(\sigma \)  and \(\dot{\sigma }\)  is upper bounded by constant, respectively. Exploring the structure of \(||\sigma ||\)  from (REF ) it can be easily inferred that such constant bound assumption on the uncertainties, whether known or unknwon, puts a restriction on the states a priori. Moreover, the switching gain in [5]}-[2]} suffers from overestimation-underestimation problem.
